1. Field of the Invention
The invention relates to a chain extender additive package for thermoplastic condensation polymers. More particularly the invention relates to an additive package comprising a water-bearing particulate and a chain extending agent for reducing the molecular weight loss of a thermoplastic condensation polymer during a heated process, an improved method for reducing the molecular weight loss of a thermoplastic condensation polymer during a heated process and a method for forming a thermoplastic condensation polymer. Even more particularly, the invention relates to an additive package comprising titanium dioxide and a multifunctional epoxy chain extending agent for combining with thermoplastic condensation polymers.
2. Description of the Related Art
The melt extrusion of thermoplastic condensation polymers, such as polyethylene terephthalate (PET) polyester, into shaped structures such as tubing, pipe, wire coating or film is accomplished by well-known high temperature procedures wherein a rotating screw pushes the viscous polymer melt through an extruder barrel into a die in which the polymer is shaped to the desired form, and is then subsequently cooled and solidified into a product, that is, the extrudate, having the general shape of the die. In film blowing processes, as an extruded plastic tube emerges from the die the tube is continuously inflated by air, cooled, collapsed by rolls and wound up on subsequent rolls.
Chain extending agents are well-known thermoplastic condensation polymer additives that “zip-up” the polymer molecules, increasing molecular weight in the final polymer. Chain extending agents are often used in condensation polymer reactions in which the growth of a polymer chain proceeds by condensation reactions between molecules of all degrees of polymerization accompanied by the formation of low-molar-mass by-products(s). Chain extending agents are capable of reacting with the condensation polymers in such a way that diminishes molecular weight loss of the condensation polymer during subsequent heated processes such as injection molding and extrusion. Even though chain extending agents are capable of reducing condensation polymer molecular weight loss during thermal processes, molecular weight loss is still a problem.